A1205 ALLEGRO [Allegro MicroSystems], A1205 Datasheet - Page 8

• Manufacturer Part Number: A1205
• Description: Continuous-Time Bipolar Switch
• Manufacturer: ALLEGRO [Allegro MicroSystems]

A1205
the field is reduced beyond the B
back to the low state.
The typical output behavior of the A120x devices is latching.
However, the A120x family is designed to attain a small hys-
teresis, and thereby provide more sensitive switching. Although
this means that true latching behavior cannot be guaranteed in all
cases, proper switching can be ensured by use of both south and
north magnetic fields, as in a ring magnet. The hysteresis of the
A120x family allows clean switching of the output, even in the
presence of external mechanical vibration and electrical noise.
Bipolar devices adopt an indeterminate output state when pow-
ered-on in the absence of a magnetic field or in a field that lies
within the hysteresis band of the device.
For more information on Bipolar switches, refer to Application
Note 27705, Understanding Bipolar Hall Effect Sensors.
Figure 2. Continuous-Time Application, B < B
Position 1, power is applied to the device. Position 2, the output assumes the correct state at a time prior to the maximum Power-On Time, t
The case shown is where the correct output state is HIGH . Position 3, t
valid, a control unit reads the output. Position 5, power is removed from the device.
V
V
OUT
CC
OP
level, the device switches
1
RP
.. This figure illustrates the use of a quick cycle for chopping V
2
t
PO(max)
PO(max)
3
Continuous-Time Bipolar Switch
CONTINUOUS-TIME BENEFITS
Continuous-time devices, such as the A120x family, offer the
fastest available power-on settling time and frequency response.
Due to offsets generated during the IC packaging process, contin-
uous-time devices typically require programming after packaging
to tighten magnetic parameter distributions. In contrast, chop-
per-stabilized switches employ an offset cancellation technique
on the chip that eliminates these offsets without the need for
after-packaging programming. The tradeoff is a longer settling
time and reduced frequency response as a result of the chopper-
stabilization offset cancellation algorithm.
The choice between continuous-time and chopper-stabilized
designs is solely determined by the application. Battery manage-
ment is an example where continuous-time is often required. In
these applications, V
in order to conserve power (refer to figure 2). The duty cycle
is controlled by the power-on time, t
has elapsed. The device output is valid. Position 4, after the output is
Output Sampled
4
CC
is chopped with a very small duty cycle
5
115 Northeast Cutoff, Box 15036
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 [phone]
www.allegromicro.com
CC
in order to conserve battery power.
PO
t
t
, of the device. Because
PO(max)
.
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